Alphabet of Lines
Chapter 3
Sacramento City College
EDT 300/ ENGR 306
EDT 300/306 - Basic Technical Drafting
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Alphabet of Lines
‹ The
design industry has agreed on a set of
standard lines that are used to represent
various objects.
‹ The
American Society of Mechanical
Engineers (ASME) has developed this
standard which is accepted throughout the
industry.
‹ Written down in a standards manual.
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Alphabet of Lines
‹ The
Alphabet of Lines
‹ reveals
‹ Shape
‹ Size
‹ Hidden
surfaces
‹ Interior detail
‹ Alternate positions
‹ Etc.
‹ of
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parts, etc.
Alphabet of Lines
‹ The
Alphabet of Lines
‹ Look different.
‹ Some are
‹ Thin
width
‹ Medium width
‹ Thick width
‹ The
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various lines are easily distinguishable.
Alphabet of Lines
‹ The
Alphabet of Lines
‹ Object
‹ Hidden
‹ Center
‹ Dimension
‹ Extension
‹ Phantom
‹ Break
‹ Datum
‹ Construction
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Alphabet of Lines
‹ Refer
to Handout
‹ The
Alphabet of Lines
‹ Available on Blackboard
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Line Characteristics
‹ All
lines should be dense black,
‹ Regardless of line type
‹ Regardless of width.
‹ Thin,
dense black
‹ Medium weight, dense black
‹ Thick weight, dense black
‹ Light
pencil lines tend to “burn out” during
the reproduction process.
‹ Make “fuzzy” lines on blueprint/copy.
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Line Characteristics
‹ Lines
are uniform within the line.
‹ Looks the same width all along the length
of the line.
‹ Thin
– thin all along the length
‹ Medium – medium all along the length
‹ Thick – thick all along the length
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Visible Lines
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Object/Visible Lines
‹ Object/Visible
Lines
‹ Show the object.
‹ Show the outline of the the visible edges or
contours of an object that can be seen by
an observer.
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Object/Visible Lines
‹ Object/Visible
Lines
‹ Should stand out sharply when contrasted
with other lines on the drawing.
‹ Object/Visible
‹ Medium
Lines - Spacing and Size.
width.
‹ Continuous line (no dashes)
‹ Dense black.
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Visible Lines
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Hidden Lines
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Hidden Lines
‹ Hidden
Lines
‹ Show
‹ Edges
‹ Surfaces
‹ Corners
‹ of
an object that are concealed from the
view of the observer.
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Hidden Lines
‹ Hidden
Lines
‹ Spacing and Size
‹ Thin
lines.
‹ Evenly space short dashes
Approximately 1/8” long,
‹ Spaces 1/32” long.
‹
‹ Dense
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black.
Hidden Lines
‹ Hidden
Line “Rules”
‹ 1. Start and end with a dash.
‹ 2. If a hidden line is a continuation of a
visible line then a gap is shown.
‹ 3. A gap is also shown when a hidden line
crosses but does not intersect another line.
‹ Hidden
lines should be omitted when they are
not needed for clarity.
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Hidden Lines
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Center Lines
EDT 300/306 - Basic Technical Drafting
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Center Lines
‹ Center
Lines
‹ Show
‹ 1.
Axes of symmetrical parts
‹ 2. Centers of circles and
‹ 3. Paths of motion.
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Center Lines
‹ Center
Lines - Spacing and Size.
‹ Thin
lines.
‹ Alternating long and short dashes.
The long dash (3/4” to 1-1/2”)
‹ The short dash (1/16” to 1/8”)
‹
‹ Dense
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black.
Center Lines
‹ Center
Lines “Rules”
‹ 1. Center lines intersect at the short
dashes.
‹ 2.
Center lines extend only a short distance
past the object.
‹ 3.
Center lines start and end with a long
dash.
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Center Lines
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Dimension Lines
Extension Lines
Leaders
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Dimension Lines, Extension Lines and Leaders
‹ Dimension
lines
‹ Indicate the size and direction of
dimensions.
‹ Are terminated by arrowheads.
‹ Dimension
‹ Thin
Lines - Spacing and Size
lines.
‹ Continuous.
‹ Dense black.
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Dimension Lines, Extension Lines and Leaders
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Dimension Lines, Extension Lines and Leaders
‹ Extension
lines
‹ Indicate the termination of a dimension.
‹ Extend from approximately
‹ 1/16
inch from the object to
‹ 1/8 inch beyond the last arrowhead.
‹ Extension
‹ Thin
Lines - Spacing and Size
lines.
‹ Dense black.
‹ Continuous lines.
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Dimension Lines, Extension Lines and Leaders
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Dimension Lines, Extension Lines and Leaders
‹ Leaders
‹ Are
drawn to notes or identification
symbols used on the drawing.
‹ Start with 1/8 “shoulder”
‹ End with arrowhead.
‹ Leaders
‹ Thin
- Spacing and Size
lines.
‹ Continuous lines.
‹ Dense black.
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Leader Lines
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Cutting Plane Lines
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Cutting Plane Lines
‹ Cutting
Plane Lines
‹ Indicate the location of the edge view of
the cutting plane.
‹ Cutting
Plane Lines - Spacing and Size
‹ Thick
line.
‹ Dense black.
‹ Two
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forms are approved for general use.
Cutting Plane Lines
‹ Cutting
Plane Lines
‹ First Form
‹ Alternating
long dashes (3/4” to 1 1/2”) and
‹ pairs of short dashes (1/8” with 1/16” space).
‹ Second
‹ Equal
‹ Both
Form
dashes 1/4” in length.
forms
bent at 90o and
‹ Ends are terminated by arrowheads to indicate
the direction of viewing of the section.
‹ Arrow stems are continuous lines.1
‹ Ends
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Cutting Plane Lines
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Section Lines
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Section Lines
‹ Section
Lines
‹ Represent surfaces exposed by a cutting
plane passing through an object.
‹ Sometimes called
‹ “cross-hatching”.
‹ “hatching”
‹ Drawn
pencil.
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at an angle of 45o with a sharp 2H
Section Lines
‹ Section
Lines - Spacing and Size
‹ Thin
lines
‹ Continuous lines.
‹ Dense black.
‹ Space
about 1/8” apart.
‹ small
‹
‹
Space lines close together
large drawings - 3/16”
‹
Space lines further apart.
‹ Make
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drawings - 1/32
line spacing uniform.
Section Lines
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Break Lines
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Break Lines
‹ Break
lines
‹ Show the limit of a partial view of a broken
section.
‹ For short breaks,
‹a
thick line is drawn freehand.
‹ Usually used for mechanical work.
‹ For
‹A
large breaks
long, thin line joined by freehand “zig-zags”.
‹ Usually used for architectural work.
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Break Lines
‹ Break
Lines - Spacing and Size
‹ Thick.
‹ Dense
black.
‹ Freehand.
‹ Continuous.
‹ Thin
‹ Dense
black
‹ Straight line with freehand “zig”
‹ Continous.
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Break Lines
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Phantom Lines
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Phantom Lines
‹ Phantom
lines:
‹ Show
‹ Alternate
positions.
‹ Repeated details.
‹ Paths of motion.
‹ Phantom
‹ Thin
Lines - Spacing and Size
lines.
‹ Dense black.
‹ Long dashes 3/4” to 1-1/2” in length with
alternating with pairs of short dashes 1/8” long
with 1/16” spacing between the dashes.
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Phantom Lines
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Datum Lines
EDT 300/306 - Basic Technical Drafting
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Datum Dimensions
‹ Datum
Lines
‹ Show
‹ Lines
‹ points
‹ surfaces
‹ assumed
that are
to be accurate.
‹ Are placed on drawings as datum
dimensions since they may be used for
exact reference and location purposes.
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Datum Dimensions
‹ Datum
Lines - Spacing and Size
‹ Thin
lines.
‹ Dense black.
‹ Thin, long dashes - 3/4” to 1-1/2” long
‹
alternating with
‹ Pairs
‹
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of short dashes - 1/8” long
1/16” spacing between the dashes.
Construction Lines
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Construction Lines
‹ Construction
Lines
‹ Used to lay out all work PRIOR to drawing
ANY object lines.
‹ Drawn very light so they will not reproduce
when making a blue print.
‹ (They
should not be visible when viewing
beyond an arm’s length from the drawing.)
‹ Construction
‹ Thin
Lines - Spacing and Size
lines.
‹ Light gray lines.
‹ Draw with very hard pencil 2H, 3H, 4H.
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Border Lines
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Border Lines
‹ Border
lines
‹ Are the “frame” of the drawing.
‹ Spacing
and Size
‹ Thickest
lines.
‹ Dense black.
‹ Continuous.
‹ Border
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lines are the heaviest of all lines.